The present invention relates to a charging paddle for charging batteries of electric vehicles.
A typical electric vehicle has a receptacle housing a secondary coil. To initiate charging of a battery in the vehicle, a charging paddle, which includes a primary coil, is inserted into the receptacle. The charging paddle is attached to the distal end of a cable connected to an electricity supplying apparatus. Specifically, the supplying apparatus converts the voltage and frequency of commercial alternating current into a current having a voltage of 430 volts and a high frequency of 100 kHz to 370 kHz. The converted current is supplied to the primary coil in the charging paddle by the cable. The primary coil induces an electromotive force in the secondary coil in the receptacle, which charges the vehicle battery.
To shorten the time required for charging, or to perform a boosting charge, charger couplings that transmit a current of a relatively great power, for example, a power of 80 kW, have been developed.
However, a higher charger coupling current results in a greater primary coil current, which causes the primary coil to generate a great amount of heat. The heat may damage devices about the primary coil and deform resin members. To solve this problem, a charging paddle 60 disclosed in Japanese Unexamined Patent Publication No. 7-169628 has a multi-layered coolant conduit 62 (only one of the layers is shown) for cooling a primary coil (not shown). As shown in FIG. 11, the charging paddle 60 is connected to a cable 61. Coolant is supplied from the cable 61 to the paddle 60. The coolant flows along arrows in the coolant conduit 62 and back to the cable 61. The primary coil is located either inside or outside the coolant conduit 62. In other words, the coolant conduit 62 and the primary coil are arranged in direction perpendicular to the plane of the paddle. Heat generated by the primary coil during charging is transferred to the coolant flowing in the conduit 62.
Japanese Unexamined Patent Publication No. 8-64442 discloses a charging paddle having a space for conducting coolant in a primary coil. Coolant flows through the space to cool the primary coil and a secondary coil.
A primary coil must be connected to wiring that supplies electricity. In FIG. 11, lines in the cable 61 are connected to the primary coil. The joint between the lines and the primary coil must be electrically insulated from the coolant conduit 62 to prevent electricity from leaking.
However, the coolant conduit 62 has a plurality of conduit units arranged in the radial direction of the core 63. Therefore, the joint between the primary coil and the electric line overlaps the coolant conduit 62 in the direction perpendicular to the plane of the paddle, which increases the thickness of the charging paddle 60. Also, in the charging paddle of the Publication No. 8-64442, the space provided for the coolant liquid increases the thickness dimension of the charging paddle. The size of the receptacle must be increased, accordingly. The receptacle will therefore take up a large space in the vehicle.